Fuze



n June 23, 1959 J. E. HENDERSON i 2,892,093

FUzE l Filed Dec. 30, 1944 3 Sheets-Sheet 1 FIG. 2

`|NvENToR 3A BY ATTORNEY June 23, 1959 Filed Dec. 30. 1944 All@ J. E. HENDERSON rFuzxs:

3 Sheets-Sheet 2 INVENTOR JSEP' HENERSN ATTORNEY June 23, 1959 J, E, HENDERSON 2,892,093

l FuzE Y Filed Dec. 30, 1944 s sheets-sheet s s l/N sH//v/NG l/v FORWARD F I6. 4 REG/0N 0F s/GHr aL//vas ONE /NPur c/ncu/r ranafr ENTER/NG HEAR REG/olv 0F s/GHT masa-Rs Fuzf INVENTOR JSEPH E. HENDERSON ATTORNEY United States, Patent iice UnitedStates of America as represented -by the Secretary of the Navy Application December 30, 1944, Serial No. 570,689 11 Claims. (Cl. 250-209) This invention relates Ito photoelectric devices and circuits, particularly as they are used in light-sensitive proximity fuzes, and constitutes a further development of the invention disclosed rinV copending-application by Joseph E. Henderson, Lawrence R. Hafstad Vand Richard B. Roberts, Serial No. 568,020, led December 13, 1944, entitled Fuze An important object of the invention is to provide an yimproved photoelectric proximity fuze construction whose effectiveness is not destroyed when it is subjected to the direct rays of the sun or other intense illumination, and lwhich will, even though (andwhile) subjected to such intense illumination, remain responsive to the relatively lsmall light differences which occur when the fuze approaches a target. 4` Another object is to provide a photoelectric fuze with two photocells, each of which receives light from the same lens but at a different angle. L

A further object is to provide a photoelectric fuze employing two lenses and two photocells, the look forward angle of each lens being differ-entr.

' An additional object is to provide a novel circuit for Aa photoelectric proximity fuze having a double field of `View, and to incorporate in the fuze operating characteristics suchwthat the fuze will be red when a Vtarget is viewed in either eld, even -though the other eld may 'be temporarily inoperative.

"j vOther objects will appear in lthe course of the following description, taken in conjunction with the 'drawings forming apart hereof, in which Y v Fig l is a longitudinal part section of a photoelectric proximity fuze constructed .m accordance with the principles of the present invention;`

Fig.4 2 is a longitudinal partV section ofa somewhat 'modied construction incorporating two lenses and two 'photocells; j j Y Y v Fig. 3 ,is a similar part sectional viewof another modi- Ied construction;

Fig. 4 is adiagramma-tic'perspective representation of the look-forward zones lof `the double eld-of-view of a fuze constructed in accordance with the present invention, illustrating the operative relationship of such fields with respect -to the sun and a target (shown as anl airplane); rFig. 5f-is 'a circuit diagram showing a parallel input circuit fory two photocells, as used in a fuze of the indicated'character, ,the input circuit being arranged in such' fashion as 4to 'be adapted to feed a one stage ampliiier; and

, Fig. 6 is a schematic diagram equivalent to Fig. 5, but M showing an input circuit amplifier. .Referring now :to the drawings, the mechanical ararranged to feed a two stage rangement of the parts shown in Fig. 1 will be seen to be essentially similar -to that disclosed in the aforementioned copending application. The fuze casing 1, formed of sheet metal, is linwardly `flanged at 2 at its forward end to 'carry the optical and related portions of the fuze mechanism ,witlrwhich thepreser'itinvention is concerned.

A supporting ring 3 is riveted to the fla-nge. Threadedly attached to the ring 3 and projecting forwardly therefrom Iis a tubular extension 5 formed of transparent plastic and having a partly toroidal lens surface 6. EX- tension 5 constitutes a housing for the photocells 14, 15 and related parts. In the respects thus far outlined the parts will be recognized as corresponding `to those disclosed in said copending application.

The extension 5 serves as a structural element as well as an optical element. 'The nose cap 7 is cemented or otherwise exteriorly mounted upon its forward extremity in a rigid manner to complete the uze enclosure. Female -threads are formed in the forward end of the extension to receive the cap ring 13 which retains the photocells 14, 15, housed therein. A crowned cap 16 of sheet metal -is mounted over the opening in the cap ring, these parts being united by screws (undesignated). 'Ilhe crowned cap serves as a nose shield and as an abutment and retainer for spring 17, which prevents vibration of the photocells and takes up any clearance therebetween. Formed integrally with the plastic extension 5 and positioned to receive light rays entering the lens from any angle within a predetermined angular range is an inwardly projecting portion 20 of annular form and wedge-shaped cross section whose lower surface is adapted to serve as a reflector, portion 20' thus constituting an annular prism.

The interior surface of -the plastic extension is masked with opaque paint or the like except in the slit-'like unpainted areas 21, 22, the former positioned to admit light from the reflecting surface of the prism section 20 when such light `enters from any angle within the limits indicated by the lines 23-23. Light rays thus admitted are totally reflected upwardly (by inward reection from the bottom surface of annular prism 20) through the sidewall of forward photocell 14, to impinge the plane cathode 25 of that cell. The light is refracted in passing through the upper surface of the wedge-shaped reflector portion 20. The rear of such reiiector portion will be seen to comprise the slit-forming unpainted area 21. The anode of photocell 14 is indicated at 27.

`The similar photocell 15 also has a plane cathode 29, which may be of disc or other suitable shape, its anode 30 being similar to anode 27. Cells 14 and 15 are of the special rugged design disclosed in copending application Serial No. 570,691, now abandoned, tiled by me jointly with Charles C. Lauritsen and Lawrence R. Hafstad, under date of December 30, 1944, entitled, yRugged Phototube, but are shortened to be even more rugged, as well as to facilitate placing the ca-thodes relatively close together so that light passing through a single lens can be readily directed upon the two cathodes.

Light rays striking lens 6 at any angle between the Vlimits indicated by lines 24-24, are directed by the lens and slit 22 upon the surface Vof cathode 29. A metal disc 32 separates the cells to act as a light screen. VThis ensuresv separation of the two beams of light so that light from only oneY beam will strike `the cathode of a `given photocell. Anodes 27, 30 Yare connected in parallel, either through the common metal plate 32 or by means of a wire as 33. A'suitable lead 34, connected Vto disc 32 and thereby to both anodes, is brought out forconnection in a suitable circuit, and leads 35, 36 are connected tothe metal exhaust tubes 37, 38 to provide connections to the cathodes 25, 29, respectively, lead 35 being brought to the rear through a bore 39 in extension 5.

An alternative construction, using two lenses instead of one, is shown in Fig. 2. The top assembly of this fuze, including spring 17A, nose shield 16A and nose cap 7A is substantially the same as that shown and described in the previously tiled application irst abovementioned. vand will 4bessen to be functionally` equivalent to the corresponding parts of the embodiment of Fig. 1 hereof. In this case, however, two integrally molded toroidal lens portions 6A, 6B are formed upon the transparent extension A, of Lucite or similar material, and two photocells 14A, 15A are arranged in the fuze in a tandem arrangement as shown. These photocells are also of the rugged cartridge type, having metal, end caps serving as supports for and as connectors to the anodes 27A and 30A respectively and the cathodes 25A and 29A respectively. Insulating ring 32A is axiallyA slidable in the cylindrical interior of the lens body and serves as a spacer between the two photocells, which are retained and urged thereagainst by spring 17A and threaded ring 3A, the latter screwed into the extension body 5A. Suitable connections or leads are similarly provided. The lens extension, as shown, is fastened to the fuze casing 1A bymeans of screws (undesignated).

The inner surface of the double lens extension sleeve 5A is opaque except for circular transparent slits 21A and 22A through which light rays within Zone 23A- 23A and 24A-24A are respectively directed by theA portions 6A, 6B. As shown, the look-forward angle of the leading lens-slit combination may be about and that of the rear lens-slit combination about 23, although this may of course be varied at will, the angles chosen being determined by the velocity and the fragment velocity characteristics of the particular projectile.

In the further modification illustrated in Fig. 3, a double field of View is attained with a single lens and two slits, analogously to the arrangement of the embodiment first described, but a single special phototube is used having two cathodes, 25C, 29C, and two anodes, 27C, C, within a single envelope. The envelope is defined by two coaxial glass tube sections 41, 42, forming a single enclosure whose ends are defined by sheet metal caps 43, 44. A cathode 29C is carried by the rear cap 44 and an anode 27C by the forward cap, also in similar fashion, but these elements do not cooperate with one another. A centrally perforate web or partition 45 ex. tends across the interior of the cell, being held between and serving to align the abutting ends of the tubing sections 41, 42. A light-sensitive cathode surface 25C is formed on the forward or upper surface of the web to cooperate with anode 27C, while the lower surface of the web acts as an anode for cooperation with cathode 29C. In order to permit using a circuit such as disclosed herein, the web 45 must be formed of insulating material, with separately applied anode and cathode surfaces. Alternatively, a circuit such as one of those disclosed in the copending application of Thomas M. Marion and John F. Streib, Serial No. 575,108, filed Ian. 29, 1945 now abandoned, may be used, in which event, the photocells being in series, a simple metallic web may be used, which thus furnishes electrical connection between the anode and cathode portions carried by its opposite sides. Other parts analogous to those already described are designated by like reference characters, distinguished by the addition of the letter C to each, and require no detailed redescription.

In operation, with either the single lens of Figures 1 and 3 or the double lens of Fig. 2, if the sun or other bright source directs strong light upon one photocell cathode, to blind it, i.e., more or less to short circuit it, then due to the difference of the look-forward angles and the narrow zones of light transmission, the other photocell will still be effective to make the fuze sensitiveto small light changes.

The separation of the two zones of light transmission or sight is clearly shown in Fig. 4, which illustrates: a projectile traveling somewhere between the sun and an airplane target. If the forward zone of sight, A, receives direct rays of the sun, the rear zone of sight B is still effective in responding to a change of light produced by airplane 50 when projectile SS'passes near it.

'I'hecircuits shown in Figs. 5 ando illustratesuitabl'e methods of connecting the photoelectric elements with respect to the input circuit of a thermionic amplifier, whose electron tube T is adapted to feed additional elements forming no part of the present invention and by means of which the explosive contents of the projectile are adapted to be detonated when a pulsation or current variation of greater than a predetermined magnitude is created by actuation of one of the photocells. For the purpose of detonating the charge, the output of the photocell circuit may of course be amplified in any suitable manner, and the circuits of Figs. 5 and 6 accordingly show only the first stage of an amplifier arrangement corresponding to that disclosed in the copending application first above-mentioned.

In Fig. 5, photocells 14 and 15 have their anodes connected in parallel by conductor 16, which is connected to the positive terminal of battery or other potential source B, the. negative terminal of which is grounded through conductor 47 to which one terminal of nonlinear impedance V1 is connected. The other terminal of this impedance is connected to cathode 25 of photocell 14, through resistance or impedance L1 connected in series. Similarly, cathode 29 of photocell 15 is connected to one terminal of nonlinear resistor or impedance, V2, through series-connected resistance or impedance L2. The other terminal of nonlinear resistor V2 is connected to resistor V1 and ground, by means of conductor 48, the photocells thus being connected in parallel.

Potential fluctuations across resistance V1 are impressed upon grid 51 of tube T by means of condenser C1 `connected as shown. Similarly, potential fluctuations across resistor V2 are impressed upon grid 51 by means of condenser C2, one terminal of which is connected to a terminal of condenser C1, the other terminals of the two condensers being connected to the respective resistors as indicated. Grid leak G is provided in the usual manner.

In operation, the photocells 14 and 15 will usually be approximately equally illuminated so that a sudden fluctuation of light intensity impressed upon either cell will result in a voltage pulse across the corresponding resistor which is coupled to the grid of tube T by the associated condenser. If, however, one photocell is subjected to very strong light, so that it is effectively short circuited due to copious electron emission, and if the other photocell is normally illuminated, then the latter photocell can still produce a pulse in the grid circuit due to a fluctuation of light intensity. This is possible since the limiting resistance or impedance (L1 or L2) in series with the flooded photocell prevents the signal from being short circuited through the connected cell. These impedances, by limiting the steady current flowing through the nonlinear resistors, also serve to maintain the differential impedance of the nonlinear resistors at a high value, thus preventing the signal from being short circuited through the nonlinear resistor connected with the ooded photocell.

Analysis and experiment indicate that with the two photocells equally illuminated the sensitivity of the circuit is about one-half that of the corresponding input circuit using a single cell as disclosed in the prior application first above referred to. If one photocell is flooded the sensitivity of the operative part of the circuit is still slightly lower. This yloss of sensitivity can be compensated for, if desired, by the use of a two stage amplifier. Inthis case, as shown in Fig. 6, the nonlinear resistors V1 and V2 and photocells 14 and 15 are reversed in position with respect to grid 51 to compensate for the 180 phase shift of the additional amplifier stage. This is to ensure that the device Will operate on a pulse caused by a decrease of light, since it has been found that greater sensitivity is. obtainable in this way.

While it will be `apparent that the preferred embodiments of my invention herein described are well calculated adequately to fulll the objects and advantages first lasagnes bove-sttedLit be apparent that the invention is susceptible to variation, modili'cation yand change within the spirit and scope of the subjoined claims. I claim: l j l,

1. In vaphotoelectric proximity fuze, an amplifier includingjanf electron tube having a thermionic cathode, an" anode, anda control element, a pluralityof photoelectric' input means coupled to said amplifier and each including a photocathode, means for directing :light from a. given; direction A against one of said photocathodes, means`for directing light VVfrom another direction against another; of said, ph,otocathodes, anode means ,arranged to coact with said photocathodes, a limiting resistor operatively appurtenant to and in series'i'with each of said photocathodes and said anode means, each of said photocthodes and its appurtenant limiting resistor comprising a series circuit, a non-linearresistor in each of said series circuits, said series circuits being arranged in shunt coupled to said control element andthermionic cathode, whereby the bias imposed upon the control element of the electron tube may be varied in response to changes in the extent of illumination of one photocathode, independently of the illumination of the other of Such photocathodes, the limiting resistors being of such proportions that short circuiting of one of said photoelectric means by intense illumination of its photocathode is incapable of short circuiting a signal imposed upon the other of said photocathodes.

2. In a photoelectric proximity fuze, an amplifier including an electron tube having a thermionic cathode, an anode, and a control element, a plurality of photoelectric means coupled to said amplifier, each of said means including a photocathode, means for directing light from a given direction against one of said photocathodes, means for directing light from another direction against another of said photocathodes, anode means arranged to coact with said photocathodes, a limiting resistor operatively appurtenant to and in series with each of said photocathodes and with said anode means, each of said photocathodes and its appurtenant limiting resistor comprising a series circuit, a non-linear resistor in each of said series circuits, said series circuits being arranged in shunt with one another, condensers connecting said non-linear resistors to said control element while preventing access of steady potential to said control element, a source of current connected to said aforementioned circuits including the photoelectric means and nonlinear resistors in such manner that current may ow through said circuits when the photoelectric means is energized, whereby a sudden decrease or cessation of illumination of one of said photocathodes produces a pulse adapted to aiect the potential applied to the control element.

3. In a photoelectric proximity fuze, an amplifier including an electron tube having a cathode, an anode, and a control element, a plurality of shunt-connected photoelectric input means coupled to said amplifier and each including a photocathode, means for directing light from a given direction against one of said photocathodes, means for directing light from another direction against another of said photocathodes, anode means coacting with said photocathodes, a limiting resistor appurtenant and arranged in a control circuit with each of said photoelectric input means, a current source connected to the control circuits to thereby maintain a current ilow therethrough when light impinges on the photocathodes, and a nonlinear resistor also incorporated in each of said control circuits in series with the limiting resistor thereof, the control grid of the electron tube being operatively connected to each of said control circuits at a point between the two resistors thereof.

4. In a photoelectric proximity fuze, an amplifier including an electron tube having a cathode, an anode,

6 t "and Va control element, a plurality of shunt-connected Vphotoelectric4 nieans coupled to said amplifier' and each including a photocathode, means for directing light from a given irectio'n against one of said photocathodes, ,Iiiealis for. directing light from another direction against .another of said photocathodes, anode means coacting with said photocathodes, a limiting resistor appurtenant and arranged iri a control circuit with each of said photoelectric input means, a current source connected to tlie Vcontrol circuits to thereby maintain a current flow therethrough when light irnpinges on the photocathodes, and ia nonlinear lresistor also incorporated in each of said `control circuits in series with thelimiting resistor thereof, and means including a grid condenser for each such cir- "cuit' 'coupling the control element to each such circuit at aV pointbetween the limiting resistor and nonlinear vresistor thereof. l

5.., YIn a photoelectric proxir'nityA fuz'e, an amplifier including a'n electron tube having a cathode, an anode,

Vand a 4control element, a plurality of shunt-connected photoelectric means coupled to said ampliiier and each including a photocathode, means for directing light from a given direction against one of said photocathodes, means for directing light from another direction against another of said photocathodes, anode means coacting with said photocathodes, a limiting resistor appurtenant and arranged in a control circuit with each of said photoelectric input means, a current source connected to the control circuits to thereby maintain a current liow therethrough when light impinges on the photocathode, and a nonlinear resistor also incorporated in each of said control circuits in series with the limiting resistor thereof, the control element of the electron tube being operatively connected to each of said control circuits at a point between the limiting resistor and nonlinear resistor thereof, said control circuits being connected in parallel with the source of current.

6. In a proximity fuze for a projectile, photosensitive means comprising a plurality of photocathodes and anode means associated with said cathodes, means for directing light from a predetermined angular direction with respect to the longitudinal axis of the projectile on one of said photocathodes, means for directing light from a different angular direction with respect to the longitudinal axis of the projectile on another of the photocathodes, and means connected to said photosensitive means for producing a fuze operation initiating pulse only in response to a change within predetermined limits of the light incident on either one of the photocathodes.

7. In a proximity fuze for a projectile, photosensitive means comprising a plurality of photocathodes and anode means associated with said cathodes, means for directing light from a predetermined angular direction with Vrespect to the longitudinal axis of the projectile on one of said photocathodes, means for directing light from a dilerent angular direction with respect to the longitudinal axis of the projectile on another of the photocathodes, and means including a non-linear resistance in series with each of the several anode-cathode paths of said photosensitive means for producing a fuze operation initiating pulse only in response to a change Within predetermined limits of the ylight incident on either one ofthe photocathodes.

8. In a proximity fuze, photosensitive means comprising a plurality of photocathodes, means for directing light from a given direction against one of said photocathodes, means for directing light from another direction against another of said photocathodes, anode means coacting with said photocathodes, and means including a non-linear resistance in series with each of the several anode-cathode paths of said photosensitive means for producing a fuze operation initiating pulse only in response to a change Within predetermined limits of the light incident on either one of the photocathodes.

9. In a photoelectric device, photosensitive means comprising a plurality of photocathodes, means for directing light from a given direction against one of said photocathodes, means for directing light from another direction against another of said photocathodes, anode means coacting with said photocathodes, means connecting the several anode-cathode paths of said photosensitive means in parallel branch circuits, potential means connected across said branch circuits, a non-linear resistance in each of said branch circuits, and electroresponsive means connected to each of said branch circuits and responsive to the voltage drop across said non-linear resistances.

10. The combi-nation of claim 9 including capacitors connecting said electroresponsive means to said branch circuits whereby only changes in the voltage drop across said non-linear resistances are applied to said electroresponsive means.

11. The combination of claim 9 including limiting resistors. in each of said branch circuits to prevent shorting of a signal in one branch circuit when the photocathode in the other branch circuit is subjected to intense illumination.

References Cited in the le of thispatent UNITED STATES PATENTS Weintraub May y9,l 1922 Hardy et al Iuly 156, y1929 Breisky et al Ian. 5, 1932 Touceda Nov'. 23, 1937 Getcken Junefl, 1939 Lundstrom Oct. 22, 1940 Liebmann Dec...30, '1940 Evans et al Apr. 7, 1942 Holloway Mar. 30, -194-3 Hussey Oct. I0, 1944 FOREIGN PATENTS France Ian."4,"1939 v OTHER REFERENCES Thermistors in Electronic Circuits, Electronics Indus- 20 tries,..Ianuary 1945-,` pages 76-80. 

